merge equivalent RFF resources

[VladimirAlexiev]

As mentioned in #3148 , these are the same resource:

• utility: https://datacommons.rff.org/browser/dc/05gsw4m93mz6 = https://datacommons.rff.org/browser/eia/u/13407
• power plant: https://datacommons.rff.org/browser/dc/3lwrcytjq2k09 = https://datacommons.rff.org/browser/eia/pp/2322

However, they have distinct dcid and there's no relation between them.
Please merge these resources (the dc/ resources seem poorer than the eia/ resources), including attributes and incoming/outgoing links.